@danwentzel The Salt Lake City <==> Denver segment would probably be fairly expensive to construct, especially east of Glenwood Springs. Salt Lake City would make a good connection point for a link to Las Vegas and then LA.
@danwentzel Yes, Amtrak goes between Denver and Salt Lake City. I've ridden it. It takes an pretty much an entire 24-hour day (and Amtrak often runs really late - 12 hours late on my last ride.)